CN115647642B - Low-alloy solder powder and preparation method thereof - Google Patents
Low-alloy solder powder and preparation method thereof Download PDFInfo
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Abstract
The invention belongs to the technical field of brazing materials, and particularly relates to low-alloy brazing filler metal powder and a preparation method thereof. The low-alloy brazing filler metal powder provided by the invention comprises the following components in parts by weight: 50-55 parts of Bi, 25-30 parts of In, 15-16 parts of Sn and 0.1-0.5 part of reinforcing powder; the reinforcing powder is one of graphite powder, cubic boron nitride and aluminum oxide; the reinforcing powder is uniformly embedded In the crystal of the Bi-In-Sn brazing filler metal powder. According to the invention, the reinforcing powder is uniformly distributed in the crystal of the powder, and the reinforcing powder cannot be separated out and separated from metal in the brazing connection process due to the size effect, so that the strength of the connection joint can be effectively enhanced, the high-temperature oxidation resistance of the joint is improved, the service life of the joint is prolonged, and the method has wide application prospects in the fields of preparation of low-alloy brazing filler metal and soft brazing of brass temperature control valves in fire-fighting equipment.
Description
Technical Field
The invention belongs to the technical field of brazing materials, and particularly relates to low-alloy brazing filler metal powder and a preparation method thereof.
Background
With the rapid development of nuclear power stations, high-rise buildings, industrial electric appliances and household appliances, higher and higher requirements are put on safety fire-fighting equipment. The low alloy solder, especially Bi-In-Sn low alloy solder with the temperature of 80-90 ℃, is mainly used for connecting brass temperature control valves of fire-fighting equipment. The brass temperature control valve is a thermosensitive element, is widely applied to safety fire-fighting equipment, and when the ambient temperature exceeds 80-90 ℃, the fusible alloy solder at the connecting part of the brass temperature control valve is immediately melted and separated, and sends out signals such as alarm or water spray to carry out safety warning. In order to meet the use requirement, the fusible alloy solder is required to have high purity, high-temperature and low-temperature alternating fatigue resistance and accurate temperature control.
At present, the existing powdery low-alloy solder is suitable for welding various brass temperature control valves, and has larger demand. However, the existing powdery low-alloy brazing filler metal is mostly prepared in an atomization mode, on one hand, complete atomization equipment is complex and expensive, powder cost is high, and on the other hand, the high-temperature oxidation resistance of the existing brazing filler metal powder connecting joint is poor, so that the brass temperature control valve which is in high-low temperature alternation for a long time is easy to oxidize and embrittle or corrode, the joint strength loss rate is high, the joint is easy to break away from or disconnect from the connecting part, the temperature control valve is invalid, and serious potential safety hazards are left.
In order to solve the above-mentioned shortcomings, it is needed to develop a low-alloy solder powder with accurate temperature control and high-temperature oxidation resistance, and at the same time, to provide a low-cost alloy solder powder preparation method which is matched with the low-alloy solder powder to meet the brazing requirement of a brass temperature control valve.
Disclosure of Invention
The first aim of the invention is to provide low-alloy solder powder, which has accurate temperature control and excellent high-temperature creep resistance, and can solve the technical problem that the existing low-alloy solder powder has poor high-temperature oxidation resistance.
The second object of the invention is to provide a preparation method of low-alloy solder powder, which does not need expensive atomization equipment, reduces equipment investment cost, has simple operation process and is suitable for industrial application.
In order to achieve the above purpose, the low alloy solder powder of the invention adopts the following technical scheme:
the low-alloy brazing filler metal powder comprises the following components in parts by mass: 50-55 parts of Bi, 25-30 parts of In, 15-16 parts of Sn and 0.1-0.5 part of reinforcing powder; the reinforcing powder is one of graphite powder, cubic boron nitride and aluminum oxide; the reinforcing powder is uniformly embedded In the crystal of the Bi-In-Sn brazing filler metal powder.
The low-alloy solder powder disclosed by the invention is composed of Bi, in, sn and reinforcing powder In a specific ratio. On one hand, the invention adopts the combination of the reinforcing powder and Bi-In-Sn, which does not influence the melting range of the solder powder, and the obtained solder powder has accurate temperature control. On the other hand, the reinforcing powder adopted by the invention does not react with high-temperature molten metal, can be uniformly embedded into the crystal of the Bi-In-Sn brazing filler metal powder, so that the Bi-In-Sn brazing filler metal powder cannot be separated out In the brazing connection process, can effectively enhance the strength of a connecting joint, improve the high-temperature durability of the joint, prolong the service life of the joint, and is suitable for brazing application of a brass temperature control valve.
The low-alloy brazing filler metal powder preferably has a particle size of 25 to 75 μm in view of ensuring brazing performance of the brazing filler metal powder.
The low-alloy brazing filler metal powder has the melting temperature of 80-90 ℃, is accurate in temperature control, and can meet the requirements of connection and safety warning of a brass temperature control valve.
The invention provides a preparation method of low-alloy solder powder, which comprises the following specific scheme:
the preparation method of the low-alloy solder powder comprises the following steps:
(1) Heating and melting Bi, in and Sn according to the proportion to obtain molten metal;
(2) Covering vegetable oil on the surface of the molten metal to form an oil film, heating and keeping the temperature of the molten metal at 100-120 ℃, scattering reinforcing powder on the surface of the molten metal oil film, and carrying out primary strong stirring treatment; then stopping heating, carrying out secondary strong stirring treatment, removing vegetable oil and redundant reinforcing powder on the surface of the metal liquid after the secondary strong stirring treatment, and then carrying out alkali washing and water washing to obtain metal balls containing the reinforcing powder;
(3) Placing the metal balls into a container containing a solvent, filling protective gas into the container, sealing, heating to assist ultrasonic grinding, removing the solvent, and drying.
The invention does not limit the melting temperature of Bi, in and Sn raw materials, and can meet the requirements of raw material melting and energy saving. Preferably, in the step (1), the temperature of the heating and melting is 85-100 ℃.
In the step (2), the invention adopts vegetable oil to form an oil film so as to play a role in isolating the atmosphere and preventing the oxidation of the molten metal. The invention does not limit the type of vegetable oil, and the boiling point is kept above the melting temperature of the brazing filler metal, and the vegetable oil is not carbonized and volatilized in the whole melting and stirring process. Preferably, the vegetable oil is one or more of soybean oil, peanut oil and rapeseed oil. The thickness of the oil film is 5-10 mm.
The nano reinforcing powder can be more easily embedded into the metal crystal, so that a better reinforcing effect is achieved. Preferably, in the step (2), the particle size of the reinforcing powder is 0.8 to 2.0 μm. The reinforcing powder with the granularity range can strengthen the joint strength formed by the low-alloy brazing filler metal powder and improve the high-temperature oxidation resistance of the low-alloy brazing filler metal powder.
Further, in the step (2), the rotating speed of the primary strong stirring and the secondary strong stirring is 30-80 r/min; the time of one-time strong stirring is 8-16 min; the secondary strong stirring time is 1-5 min. The primary strong stirring is carried out under the heating and heat preserving conditions, the high-temperature strong stirring treatment is carried out, and the secondary strong stirring is carried out after the heating is stopped, and the low-temperature strong stirring is carried out. The invention leads the dendrite network framework of the metal liquid to be crushed preliminarily by high-temperature strong stirring, and the stirring vortex is involved in the reinforcing powder; and then carrying out low-temperature strong stirring, wherein the reinforcing powder is used for further physically separating alloy liquid in the low-temperature strong stirring process to form metal balls.
In the step (3), protective gas is introduced to form protection for the metal balls, so that the oxidation of the metal balls is avoided. Preferably, the pressure of the shielding gas is 0.5-2.0 MPa. The shielding gas may be nitrogen, helium or other conventional shielding gases. The shielding gas is more preferably nitrogen from the viewpoint of cost reduction.
In the step (3), the solvent is any one of absolute ethyl alcohol and acetone. More preferably, the solvent is absolute ethanol. The container used in this step is a sealable container, such as a sealable stainless steel container.
In the invention, the heating-assisted ultrasonic grinding treatment can be realized by the following steps: placing the sealed container on an electric heating workbench, setting heating temperature, contacting the top of the container with an ultrasonic vibration rod, and controlling the technological conditions of the vibration rod to perform heating-assisted ultrasonic crushing treatment.
Preferably, in the step (3), the heating temperature is 60-70 ℃, the frequency of the ultrasonic wave is 26-30 kHz, the power of the ultrasonic wave is 80-120W, and the time of the heating auxiliary ultrasonic wave crushing treatment is 30-60 min.
The preparation method of the low-alloy solder powder sequentially comprises the steps of forming molten metal, metal balls and solder powder.
At present, the traditional metal brazing filler metal powder and the reinforcing powder are generally mechanically mixed to form brazing filler metal powder. Because the reinforcing powder is generally low in density, poor in affinity with metal and poor in wettability, and easily floats out of a liquid surface in the brazing connection process and is separated from the metal, the reinforcing powder is difficult to embed into a metal joint at all, and therefore the strength of the joint and the effect of resisting high-temperature oxidation cannot be effectively enhanced.
In the invention, when the reinforcing powder is introduced, on one hand, dendrites are crushed under high-speed rotation by high Wen Jianglie stirring action, and stirring vortex is involved in the reinforcing powder, so that the reinforcing powder is further separated from high-temperature molten metal; on the other hand, the size effect is utilized to enable the reinforcing powder to be mechanically embedded into the alloy liquid under the drive of vortex flow of high-speed stirring, and metal balls containing the reinforcing powder in crystals are formed after low-temperature high-speed stirring and cooling. Subsequently, the metal balls are placed in a closed container protected by a shielding gas, and the semi-solid metal balls are separated by ultrasonic crushing, thereby forming a low-alloy brazing filler metal powder.
Through the process design, the reinforcing powder can be uniformly distributed In the crystal of the Bi-In-Sn brazing filler metal powder, and the reinforcing powder cannot be separated out and separated from metal In the brazing connection process due to the size effect, so that the strength of a connection joint can be effectively enhanced, the high-temperature oxidation resistance of the joint can be improved, and the service life of the joint can be prolonged.
In addition, the preparation method disclosed by the invention is simple in process, does not need to use atomizing equipment, reduces the material input cost, and is more suitable for industrial popularization and application. Meanwhile, the invention breaks dendrite under high-speed rotation first, then breaks semi-solid metal ball by ultrasonic, the low-alloy solder powder obtained is low in cost and high in purity, and has wide popularization and application prospect in the field of preparation of low-alloy solder and soft soldering of brass temperature control valve in fire-fighting equipment.
Drawings
FIG. 1 is a schematic diagram of the structure of a low alloy brazing filler metal powder according to the present invention;
FIG. 2 is a schematic structural view of a low-alloy solder powder preparing apparatus according to the present invention;
FIG. 3 is a macroscopic morphology of a joint obtained by welding the low alloy brazing filler metal powder of the present invention (left) and the existing brazing filler metal powder of comparative example 1 (right) after high temperature aging treatment;
FIG. 4 is a microstructure and spectrum analysis result of a joint obtained by conventional brazing filler metal powder welding of comparative example 1 after aging treatment;
FIG. 5 shows the microstructure and spectrum analysis results of the joint obtained by welding the low alloy brazing filler metal powder according to example 1 of the present invention after aging treatment;
FIG. 6 shows the macro morphology and micro morphology of the metal balls obtained in the preparation process of the low alloy brazing filler metal powder of example 1 of the present invention;
FIG. 7 is a morphology chart of a metal microstructure after melting of the solder powder of comparative example 2;
wherein, in fig. 2: 1-an electric heating workbench, 2-molten metal, 3-a stirring head, 4-a mixed layer of oil liquid and reinforcing powder, 5-a stirring rod, 6-a power supply, 7-an ultrasonic vibration rod, 8-a solvent and 9-a metal ball.
Detailed Description
The technical scheme of the invention is further described below with reference to the specific embodiments.
The low-alloy brazing filler metal powder has a structure schematically shown in figure 1. In fig. 1, the reinforcing powder is uniformly embedded inside the crystal of the Bi-In-Sn solder powder.
Fig. 2 is a schematic structural view of a low alloy brazing filler metal powder preparing apparatus. In fig. 2, the left side is a stirring device, and the right side is a heating-assisted ultrasonic grinding device. In the left diagram, the electric heating workbench 1 is used for heating the molten metal 2, the power supply 6 is started, and the stirring rod 5 is used for driving the stirring head 3 to rotate so as to stir the mixed layer 4 of the oil liquid and the reinforcing powder and the molten metal 2. In the right view of fig. 2, the metal balls 9 are present in the solvent 8, and the metal balls 9 are subjected to ultrasonic pulverization treatment by the ultrasonic vibration rod 7.
The specific conditions not illustrated in the examples below were carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents and materials used in the following examples, unless otherwise specified, were conventional products obtained from commercial sources.
Example 1
The low-alloy brazing filler metal powder of the embodiment comprises the following components in parts by weight: 50 parts of Bi, 25 parts of In, 16 parts of Sn and 0.1 part of reinforcing powder. The reinforcing powder is graphite powder and is uniformly embedded In the crystal of the Bi-In-Sn brazing filler metal powder. The melting temperature range of the low-alloy solder powder is 88-90 ℃, and the granularity is 60-75 mu m.
The preparation method of the low-alloy solder powder comprises the following steps:
(1) Weighing Bi, in and Sn according to parts by weight, placing the Bi, in and Sn In a stainless steel crucible, placing the stainless steel crucible In an electric heating workbench, heating to 85 ℃ and melting into molten metal;
(2) Placing the stirring head in molten metal, adding soybean oil with the depth of 5mm for covering, and keeping the temperature of the molten metal at 100 ℃; sprinkling reinforcing powder (the granularity of graphite powder is 0.8 mu m) on the surface of a molten metal oil film, starting a stirring head to strongly stir for 8min at the rotating speed of 30r/min, turning off a heating power supply, strongly stirring for 1min at the rotating speed of 30r/min, filtering vegetable oil and redundant reinforcing powder, and obtaining the metal balls containing nano reinforcing powder through alkali washing and water washing;
(3) Filling the metal balls into a stainless steel container filled with absolute ethyl alcohol solvent, introducing nitrogen with the atmospheric pressure of 0.5Mpa, and sealing the stainless steel container; placing the sealed stainless steel container on an electric heating workbench, heating at 60 ℃ for heat preservation, enabling the top of the container to be in contact with an ultrasonic vibration rod, enabling the frequency of ultrasonic waves to be 28KHz, enabling the power to be 100W, enabling ultrasonic vibration to perform heating-assisted ultrasonic grinding treatment for 30min, finally pouring absolute ethyl alcohol, and drying to obtain the low-alloy brazing filler metal powder in the embodiment 1.
Example 2
The low-alloy brazing filler metal powder of the embodiment comprises the following components in parts by weight: 52 parts of Bi, 26 parts of In, 16 parts of Sn and 0.2 part of reinforcing powder. The reinforcing powder is cubic boron nitride and is uniformly embedded In the crystal of the Bi-In-Sn brazing filler metal powder. The melting temperature range of the low-alloy solder powder is 86-88 ℃, and the granularity is 58-60 mu m.
The preparation method of the low-alloy solder powder comprises the following steps:
(1) Weighing Bi, in and Sn according to parts by weight, placing the Bi, in and Sn In a stainless steel crucible, placing the stainless steel crucible In an electric heating workbench, heating to 90 ℃ and melting into molten metal;
(2) Placing the stirring head in molten metal, adding vegetable oil (soybean oil) with the depth of 6mm for covering, and keeping the temperature of the molten metal at 110 ℃; sprinkling reinforcing powder (granularity is 0.8 μm) on the surface of a molten metal oil film, starting a stirring head, stirring for 10min at a rotating speed of 45r/min, turning off a heating power supply, stirring for 2min at a rotating speed of 45r/min, filtering vegetable oil and redundant reinforcing powder, and washing with alkali to obtain metal balls containing nano reinforcing powder;
(3) Filling the metal balls into a stainless steel container filled with absolute ethyl alcohol solvent, introducing protective gas (nitrogen) with the atmospheric pressure of 1Mpa, and sealing the stainless steel container; placing the sealed stainless steel container on an electric heating workbench, heating at 60 ℃ for heat preservation, enabling the top of the container to be in contact with an ultrasonic vibration rod, enabling the frequency of ultrasonic waves to be 28KHz, enabling the power to be 100W, enabling ultrasonic vibration to perform heating-assisted ultrasonic grinding treatment for 40min, finally pouring absolute ethyl alcohol, and drying to obtain the low-alloy brazing filler metal powder in the embodiment 2.
Example 3
The low-alloy brazing filler metal powder of the embodiment comprises the following components in parts by weight: 53 parts of Bi, 27 parts of In, 16 parts of Sn and 0.3 part of reinforcing powder. The reinforcing powder is alumina and is uniformly embedded In the crystal of the Bi-In-Sn brazing filler metal powder. The melting temperature range of the low-alloy solder powder is 84.5-86 ℃, and the granularity is 45-58 mu m.
The preparation method of the low-alloy solder powder comprises the following steps:
(1) Weighing Bi, in and Sn according to parts by weight, placing the Bi, in and Sn In a stainless steel crucible, placing the stainless steel crucible In an electric heating workbench, heating to 100 ℃ and melting into molten metal;
(2) Placing the stirring head in molten metal, adding vegetable oil (soybean oil) with the depth of 8mm for covering, and keeping the temperature of the molten metal at 120 ℃; sprinkling reinforcing powder (particle size of 0.8 μm) on the surface of a molten metal oil film, starting a stirring head, stirring for 12min at a speed of 55r/min, turning off a heating power supply, stirring for 3min at a speed of 55r/min, filtering vegetable oil and redundant reinforcing powder, and washing with alkali to obtain metal balls containing nano reinforcing powder;
(3) Filling the metal balls into a stainless steel container filled with absolute ethyl alcohol serving as a solvent, introducing protective gas (nitrogen) with the atmospheric pressure of 1.5Mpa, and sealing the stainless steel container; placing the sealed stainless steel container on an electric heating workbench, heating at 70 ℃ for heat preservation, enabling the top of the container to be in contact with an ultrasonic vibration rod, enabling the frequency of ultrasonic waves to be 28KHz, enabling the power to be 100W, enabling ultrasonic vibration to perform heating-assisted ultrasonic grinding treatment for 45min, finally pouring absolute ethyl alcohol, and drying to obtain the low-alloy brazing filler metal powder in the embodiment 3.
Example 4
The low-alloy brazing filler metal powder of the embodiment comprises the following components in parts by weight: 54 parts of Bi, 28 parts of In, 15.5 parts of Sn and 0.4 part of reinforcing powder. The reinforcing powder is graphite powder and is uniformly embedded In the crystal of the Bi-In-Sn brazing filler metal powder. The melting temperature range of the low-alloy solder powder is 84.5-86 ℃, and the granularity is 30-45 mu m.
The preparation method of the low-alloy solder powder comprises the following steps:
(1) Weighing Bi, in and Sn according to parts by weight, placing the Bi, in and Sn In a stainless steel crucible, placing the stainless steel crucible In an electric heating workbench, heating to 95 ℃ and melting into molten metal;
(2) Placing the stirring head in molten metal, adding vegetable oil (soybean oil) with the depth of 10mm for covering, and keeping the temperature of the molten metal at 100 ℃; sprinkling reinforcing powder (particle size of 0.8 μm) on the surface of a molten metal oil film, starting a stirring head, stirring for 14min at a rotating speed of 70r/min, turning off a heating power supply, stirring for 4min at a rotating speed of 70r/min, filtering vegetable oil and redundant reinforcing powder, and washing with alkali to obtain metal balls containing nano reinforcing powder;
(3) Filling the metal balls into a stainless steel container filled with absolute ethyl alcohol solvent, introducing protective gas (nitrogen) with the atmospheric pressure of 2Mpa, and sealing the stainless steel container; placing the sealed stainless steel container on an electric heating workbench, heating at 60 ℃ for heat preservation, enabling the top of the container to be in contact with an ultrasonic vibration rod, enabling the frequency of ultrasonic waves to be 28KHz, enabling the power to be 100W, enabling ultrasonic vibration to perform heating-assisted ultrasonic grinding treatment for 55min, finally pouring absolute ethyl alcohol, and drying to obtain the low-alloy brazing filler metal powder in the embodiment 4.
Example 5
The low-alloy brazing filler metal powder of the embodiment comprises the following components in parts by weight: 55 parts of Bi, 30 parts of In, 15 parts of Sn and 0.5 part of reinforcing powder. The reinforcing powder is cubic boron nitride and is uniformly embedded In the crystal of the Bi-In-Sn brazing filler metal powder. The melting temperature range of the low-alloy solder powder is 84.5-86 ℃, and the granularity is 25-30 mu m.
The preparation method of the low-alloy solder powder comprises the following steps:
(1) Weighing Bi, in and Sn according to parts by weight, placing the Bi, in and Sn In a stainless steel crucible, placing the stainless steel crucible In an electric heating workbench, heating to 90 ℃ and melting into molten metal;
(2) Placing the stirring head in molten metal, adding vegetable oil (soybean oil) with the depth of 8mm for covering, and keeping the temperature of the molten metal at 120 ℃; sprinkling reinforcing powder (granularity is 0.8 μm) on the surface of a molten metal oil film, starting a stirring head, stirring for 16min at a rotating speed of 80r/min, turning off a heating power supply, stirring for 5min at a rotating speed of 80r/min, filtering vegetable oil and redundant reinforcing powder, and washing with alkali to obtain metal balls containing nano reinforcing powder;
(3) Filling the metal balls into a stainless steel container filled with absolute ethyl alcohol solvent, introducing protective gas (nitrogen) with the atmospheric pressure of 2Mpa, and sealing the stainless steel container; placing the sealed stainless steel container on an electric heating workbench, heating at 70 ℃ for heat preservation, enabling the top of the container to be in contact with an ultrasonic vibration rod, enabling the frequency of ultrasonic waves to be 28KHz, enabling the power to be 100W, enabling ultrasonic vibration to perform heating-assisted ultrasonic grinding treatment for 55min, finally pouring absolute ethyl alcohol, and drying to obtain the low-alloy brazing filler metal powder in the embodiment 5.
Test example 1
The low alloy solder powders of examples 1 to 5 and the existing solder powders were used to weld brass temperature-controlled elements, respectively, 10 brass temperature-controlled elements were welded to each solder powder, 5 were used to directly test joint strength, and 5 were used to test joint strength before and after high temperature aging of the joint after heat preservation at 70 ℃ for 500 hours in a box-type resistance furnace.
The method for testing the joint strength is carried out by referring to the standard GB/T11363-2008 brazing joint strength test method.
Comparative example 1: the existing brazing filler metal powder comprises the following materials in parts by weight: 50 parts of Bi, 25 parts of In and 16 parts of Sn, and the preparation process is a gas atomization preparation technology. The granularity of the composite solder powder is 60-75 mu m.
Comparative example 2; the brazing filler metal powder and the reinforcing powder are directly mechanically mixed by a planetary ball mill to obtain composite brazing filler metal powder, and the composite brazing filler metal powder comprises the following materials in parts by weight: 50 parts of Bi, 25 parts of In, 16 parts of Sn and 0.1 part of reinforcing powder. The reinforcing powder is graphite powder, and the granularity of the composite brazing filler metal powder is 60-75 mu m.
The results of measuring the strength of the joint before and after aging at high temperature are shown in Table 1.
Table 1 shear strength of brass temperature control element joints
As can be seen from Table 1, in the examples of the present invention, the strength of the solder powder soldered joint was decreased with the increase of the proportion of the reinforcing powder in the solder powder, and therefore, the excessive reinforcing powder caused deterioration of the joint strength of the brass temperature control element. The strength of the joint is highest when the consumption of the reinforcing powder is 0.1 part, and the strength loss rate is lowest after high-temperature aging, namely the high-temperature creep resistance is best. The existing solder powder connection joint of the control group 1 has poor high-temperature oxidation resistance, the strength loss rate of the joint after aging treatment is up to 40%, the joint is easily separated or disconnected from the connection part in the use process, the temperature control valve is invalid, and the potential safety hazard is large. Similarly, in comparative example 2, the composite filler metal powder obtained by mechanical mixing was unable to effectively bond the reinforcing powder to the metal, and the joint strength was also significantly lowered.
Test example 2
Brass temperature control elements were soldered separately using the low alloy solder powder of example 1 and the existing solder powder of comparative example 1. Test methods and conditions: braze welding brass temperature control element test pieces (68 brass plates with the length of 80mm, the width of 20mm and the thickness of 2mm, two plates are in lap joint welding, the lap joint length of 2 mm) by adopting different brazing filler metal powder, braze welding in a furnace, insulating the braze welding test pieces in a box-type resistance furnace at 100 ℃ for 2min to obtain different brass temperature control braze welding test pieces, then placing the braze welding test pieces in the box-type resistance furnace at 70 ℃ for insulating for 500h for aging treatment, comparing macroscopic and microscopic structure morphologies of joints after aging treatment of the two brazing filler metal test pieces, and carrying out energy spectrum analysis.
Fig. 3 shows the macroscopic morphology of the joint obtained by high temperature aging of the low alloy brazing filler metal powder (left) of example 1 and the existing brazing filler metal powder (right). As can be seen from FIG. 3, the joint obtained by welding the existing solder powder has a large-area black area crosslinked into a sheet after high-temperature aging, and the joint is seriously oxidized, whereas the joint obtained by welding the solder powder in embodiment 1 of the invention has obviously less black area after high-temperature aging, and has a light oxidation degree, which indicates that the solder powder of the invention has excellent high-temperature oxidation resistance.
Fig. 4 and 5 are microscopic morphology and spectral analysis results of the joints obtained after the aging treatment of the conventional brazing filler metal powder of comparative example 1 and the brazing filler metal powder of example 1, respectively, after the brazing temperature control element was welded.
From the microscopic morphology and the energy spectrum analysis result of fig. 4, the oxygen content in the position 1 is higher, zinc, copper, indium and a small amount of bismuth in the figure are estimated to be indium oxide, zinc oxide and copper oxide, the position 2 is a bismuth-rich phase, and the position 3 is zinc oxide and copper oxide, so that the high-temperature oxidation of the joint obtained by welding the existing solder powder is serious.
As can be seen from the microscopic morphology and the spectral analysis results of fig. 5, the solder powder welded joint of example 1 has lighter color, and the main structure is bismuth-indium phase (Bi-In) and tin phase (β -Sn), and the high-temperature oxidation condition is significantly lower than that of the existing solder powder.
FIG. 6 is a graph showing the comparison of the macroscopic morphology and microscopic morphology of the metal balls obtained in the step (2) of preparing the low alloy brazing filler metal powder of example 1.
As can be seen from fig. 6, both macroscopic and microscopic structures show that the reinforcing powder is uniformly embedded inside the crystal of the Bi-In-Sn solder powder. The low-alloy solder powder of the embodiment 1 also proves that the reinforcing powder cannot be separated out and separated from metal in the brazing connection process, the high-temperature oxidation resistance is good, the high-temperature durability of the joint is good, and the joint is not easy to fail.
Test example 3
In comparative example 2, the reinforcing powder was added to the brazing filler metal powder by a mechanical mixing method, and the morphology of the microstructure of the molten metal of the brazing filler metal powder of comparative example 2 is shown in fig. 7. As can be seen from fig. 7, the black graphite reinforcing powder is extremely unevenly distributed in the metal structure, and thus, the joint strength is lowered.
In summary, the low-alloy solder powder provided by the invention can ensure that the reinforcing powder is uniformly distributed In the crystal of the Bi-In-Sn solder powder through a special process design, the reinforcing powder cannot be separated out and separated from metal In the brazing connection process, the strength of a connection joint can be effectively enhanced, the high-temperature oxidation resistance of the joint is improved, and the service life of the joint is prolonged. In addition, the invention does not need to use atomization equipment, reduces the material input cost, and the obtained low-alloy solder powder has low cost and high purity, and has wide popularization and application prospect in the fields of preparation of low-alloy solder and soldering of brass temperature control valves in fire-fighting equipment.
Finally, it should be noted that the above embodiments are merely illustrative of the technical solution of the present invention, and not limiting thereof; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.
Claims (10)
1. The low-alloy brazing filler metal powder is characterized by comprising the following components in parts by mass: 50-55 parts of Bi, 25-30 parts of In, 15-16 parts of Sn and 0.1-0.5 part of reinforcing powder; the reinforcing powder is one of graphite powder, cubic boron nitride and aluminum oxide; the reinforcing powder is uniformly embedded In the crystal of the Bi-In-Sn brazing filler metal powder;
the preparation method of the low-alloy solder powder comprises the following steps:
(1) Heating and melting Bi, in and Sn according to the proportion to obtain molten metal;
(2) Covering vegetable oil on the surface of the molten metal to form an oil film, heating and keeping the temperature of the molten metal at 100-120 ℃, scattering reinforcing powder on the surface of the molten metal oil film, and carrying out primary strong stirring treatment; then stopping heating, carrying out secondary strong stirring treatment, removing vegetable oil and redundant reinforcing powder on the surface of the metal liquid after the secondary strong stirring treatment, and then carrying out alkali washing and water washing to obtain metal balls containing the reinforcing powder;
(3) And (3) placing the metal balls into a container containing a solvent, filling protective gas into the container, sealing, heating to assist ultrasonic grinding, removing the solvent, and drying.
2. A low alloy filler metal powder as claimed in claim 1, wherein the particle size of the low alloy filler metal powder is 25 to 75 μm and the melting temperature is 80 to 90 ℃.
3. A method for preparing the low alloy brazing filler metal powder according to claim 1, comprising the steps of:
(1) Heating and melting Bi, in and Sn according to the proportion to obtain molten metal;
(2) Covering vegetable oil on the surface of the molten metal to form an oil film, heating and keeping the temperature of the molten metal at 100-120 ℃, scattering reinforcing powder on the surface of the molten metal oil film, and carrying out primary strong stirring treatment; then stopping heating, carrying out secondary strong stirring treatment, removing vegetable oil and redundant reinforcing powder on the surface of the metal liquid after the secondary strong stirring treatment, and then carrying out alkali washing and water washing to obtain metal balls containing the reinforcing powder;
(3) And (3) placing the metal balls into a container containing a solvent, filling protective gas into the container, sealing, heating to assist ultrasonic grinding, removing the solvent, and drying.
4. A method for producing a low alloy filler metal powder as defined in claim 3, wherein in step (1), the temperature of the heat melting is 85 to 100 ℃.
5. A method of producing a low alloy filler metal powder as defined in claim 3, wherein in step (2), the vegetable oil is one or more of soybean oil, peanut oil, and rapeseed oil.
6. A method for producing a low alloy filler metal powder as defined in claim 3, wherein in step (2), the particle size of the reinforcing powder is 0.8 to 2.0 μm.
7. The method for producing a low alloy filler metal powder according to any one of claims 3 to 6, wherein in step (2), the rotational speed of the primary and secondary intense stirring is 30 to 80r/min; the time of one-time strong stirring is 8-16 min; the secondary strong stirring time is 1-5 min.
8. The method for producing a low alloy filler metal powder according to any one of claims 3 to 6, wherein the pressure of the shielding gas in step (3) is 0.5 to 2.0MPa.
9. The method for producing a low alloy filler metal powder according to any one of claims 3 to 6, wherein in step (3), the solvent is any one of absolute ethyl alcohol and acetone.
10. The method for producing a low alloy filler metal powder according to any one of claims 3 to 6, wherein in step (3), the heating temperature is 60 to 70 ℃, the frequency of the ultrasonic wave is 26 to 30kHz, the power of the ultrasonic wave is 80 to 120W, and the time for the heating-assisted ultrasonic pulverizing treatment is 30 to 60 minutes.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| DE4443459C2 (en) * | 1994-12-07 | 1996-11-21 | Wieland Werke Ag | Lead-free soft solder and its use |
| CN102513720B (en) * | 2011-12-23 | 2014-05-07 | 哈尔滨工业大学深圳研究生院 | High-performance tin-based solder alloy and preparation method thereof |
| CN107009050A (en) * | 2017-06-01 | 2017-08-04 | 合肥邦诺科技有限公司 | A kind of ceramic granule reinforced composite material |
| CN108971793B (en) * | 2018-08-24 | 2021-04-23 | 云南科威液态金属谷研发有限公司 | Low-temperature lead-free solder |
| CN113215444B (en) * | 2021-04-23 | 2022-07-19 | 广东省科学院材料与加工研究所 | Nano-particle reinforced TC4 metal powder material and preparation method thereof |
| CN113215432B (en) * | 2021-04-23 | 2022-07-15 | 广东省科学院材料与加工研究所 | Nano silicon carbide particle reinforced copper-based spherical metal powder suitable for 3D printing and preparation method thereof |
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